Top: density profile of the collapsing cloud at four stages of its evolution for the Larson (Larson 1969) scenario (thick lines), and for our simple collapse model of Sect. 2.2. Bottom: ∫ n_H d t for the Larson collapse for gas cells distributed at different radius before the cloud collapse. Results for models of uniform compression assuming n_H ∝ R⁻³ (black thick line) and n_H ∝ R⁻² (black thin line) are over-plotted.